Uranium isotopes and past changes in Southern Ocean circulation

铀同位素和南大洋环流过去的变化

• 批准号: 1658445
• 负责人: Christopher Hayes
• 金额: $ 23.95万
• 依托单位: University of Southern Mississippi
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1658445&HistoricalAwards=false
• 关键词: Uranium; isotopes; past; changes; Southern

Ocean circulation has deep connections with processes around the Earth including the melting or growing of continental ice sheets. The exact mechanisms linking ocean circulation to ice sheet variability can be difficult to tease out using modern observations alone. Geologists therefore look to the past for examples of when ocean circulation changed and how those changes relate to other phenomena in past eras. In particular, it has been found that the circulation of Antarctic Bottom Water, dense water that sinks around the Antarctic continent and fills the deepest parts of the world?'s ocean, may have a very intimate link with melting of the West Antarctic Ice Sheet. The concentration of naturally-occurring uranium in Southern Ocean sediments, formed under low oxygen conditions, is a key tool that has been applied to reconstruct past circulation changes during one past warm period, ~125,000 years ago, in one area of the Southern Ocean. This project will apply this recently developed method to other areas of the Southern Ocean and to other time periods in the past (up to 500,000 years ago) in order to investigate a more robust mechanism for how circulation around Antarctica is linked to ice sheet melting and how this might change in the future. The project supports an early-career researcher as well the training of a graduate and undergraduate students in the research. Outreach will be accomplished through the development of a new course and with high school students through events such as the Ocean Sciences Bowl competition. The project will contribute to infrastructure by developing a new proxy for paleoceanography, which has the potential to better constrain models of ice sheet melting and inform on issues related to climate change and sea level rise.To more accurately reconstruct past deep Southern Ocean oxygenation conditions, and therefore Antarctic Bottom Water (AABW) circulation, the project will utilize a novel geochemical approach using the isotope composition of authigenic uranium (U-234/U-238), augmented by other redox sensitive metals (Re and Mn). This combination of measurements allows for periods of changing oxidation to be identified that elemental proxies alone could not detect. This approach will be applied in multiple Southern Ocean cores to test for reproducibility and sensitivity to varying sedimentary environments. Furthermore, the project will investigate multiple interglacial periods over the past 500,000 years to examine the response of AABW across a range of forcings and Antarctic Ice sheet extents. The result will be a robust perspective on AABW variability during interglacial periods and its relationship to external forcings (orbital configuration, CO2, Southern Ocean productivity) and West Antarctic Ice Sheet melting.

海洋环流与地球周围的过程有着密切的联系，包括大陆冰盖的融化或生长。仅凭现代观测很难弄清楚海洋环流与冰盖变化之间联系的确切机制。因此，地质学家从过去寻找海洋环流何时发生变化的例子，以及这些变化与过去时代的其他现象有何关系。特别是，人们发现南极底层水的循环，即围绕南极大陆下沉并充满世界海洋最深处的浓水，可能与南极西部冰盖的融化有着非常密切的联系。 。南大洋沉积物中天然存在的铀浓度是在低氧条件下形成的，是一种关键工具，已被用来重建南大洋某个地区过去一个温暖时期（约 125,000 年前）的环流变化。 该项目将把这种最近开发的方法应用于南大洋的其他地区和过去的其他时间段（最多 50 万年前），以研究更强有力的机制，了解南极洲周围的环流如何与冰盖融化和冰盖融化联系起来。未来这种情况可能会发生怎样的变化。 该项目支持早期职业研究人员以及研究生和本科生的研究培训。 外展活动将通过开发新课程以及通过海洋科学碗竞赛等活动与高中生一起完成。该项目将通过开发一种新的古海洋学代理来为基础设施做出贡献，该代理有可能更好地约束冰盖融化模型，并为与气候变化和海平面上升相关的问题提供信息。为了更准确地重建过去的南大洋深处氧合条件，因此，为了南极底水（AABW）循环，该项目将采用一种新颖的地球化学方法，利用自生铀（U-234/U-238）的同位素组成，并辅以其他氧化还原敏感金属（铼和锰）。这种测量组合可以识别氧化变化的时期，这是元素代理无法单独检测的。该方法将应用于多个南大洋岩心，以测试对不同沉积环境的再现性和敏感性。此外，该项目还将调查过去 50 万年的多个间冰期，以研究 AABW 在一系列强迫和南极冰盖范围内的响应。其结果将是对间冰期 AABW 变化及其与外部强迫（轨道结构、二氧化碳、南大洋生产力）和西南极冰盖融化的关系的有力视角。

项目成果

Global Ocean Sediment Composition and Burial Flux in the Deep Sea

全球海洋沉积物成分和深海埋藏通量

• DOI: 10.1029/2020gb006769
• 发表时间: 2021-02-08
• 期刊: Global Biogeochemical Cycles
• 影响因子: 5.2
• 作者: C. T. Hayes;K. Costa;R. Anderson;E. Calvo;Z. Chase;L. L. Demina;J. Dutay;C. German;Lars‐Eric Heimb
• 通讯作者: Lars‐Eric Heimb

Southern Ocean Oxygenation Changes Inferred From Redox‐Sensitive Trace Metals Across Marine Isotope Stage 11

根据海洋同位素第 11 阶段的氧化还原敏感痕量金属推断南大洋氧合变化

• DOI: 10.1029/2021gc009921
• 发表时间: 2021-08
• 期刊: Geosystems
• 作者: Rohde, E. E.;Hayes, C. T.;Redmond, N.;Glasscock, S. K.
• 通讯作者: Glasscock, S. K.

Changes in Antarctic Bottom Water Formation During Interglacial Periods

间冰期南极底层水形成的变化

• DOI: 10.1029/2020pa003867
• 发表时间: 2020-08
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: Glasscock, S. K.;Hayes, C. T.;Redmond, N.;Rohde, E.
• 通讯作者: Rohde, E.

230 Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

230 th 归一化：对量化现代和第四纪海洋沉积通量的基本工具的新见解

• DOI: 10.1029/2019pa003820
• 发表时间: 2020-02
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: Costa, Kassandra M.;Hayes, Christopher T.;Anderson, Robert F.;Pavia, Frank J.;Bausch, Alexandra;Deng, Feifei;Dutay, Jean‐Claude;Geibert, Walter;Heinze, Christoph;Henderson, Gideon;et al
• 通讯作者: et al